Make EstimateMedianVal smarter about small failures.

Instead of stopping if it encounters a "sufficient" number of transactions which don't meet the threshold for being confirmed within the target, it keeps looking to add more transactions to see if there is a temporary blip in the data.  This allows a smaller number of required data points.

src/policy/fees.cpp

@@ -231,11 +231,9 @@ double TxConfirmStats::EstimateMedianVal(int confTarget, double sufficientTxVal,
             double curPct = nConf / (totalNum + extraNum);
 
             // Check to see if we are no longer getting confirmed at the success rate
-            if (requireGreater && curPct < successBreakPoint)
+            if ((requireGreater && curPct < successBreakPoint) || (!requireGreater && curPct > successBreakPoint)) {
-                break;
+                continue;
-            if (!requireGreater && curPct > successBreakPoint)
+            }
-                break;
-
             // Otherwise update the cumulative stats, and the bucket variables
             // and reset the counters
             else {

src/policy/fees.h

@@ -88,8 +88,8 @@ private:
     static constexpr double SUCCESS_PCT = .85;
     static constexpr double DOUBLE_SUCCESS_PCT = .95;
 
-    /** Require an avg of 1 tx in the combined feerate bucket per block to have stat significance */
+    /** Require an avg of 0.1 tx in the combined feerate bucket per block to have stat significance */
-    static constexpr double SUFFICIENT_FEETXS = 1;
+    static constexpr double SUFFICIENT_FEETXS = 0.1;
 
     /** Minimum and Maximum values for tracking feerates
      * The MIN_BUCKET_FEERATE should just be set to the lowest reasonable feerate we